#!/usr/bin/perl

use strict;
use warnings;
use Getopt::Std;

my $USAGE = "$0 <old name> <new name>\n";

my %opts;
getopts("", \%opts) or die $USAGE;

if (@ARGV != 2) {
   die $USAGE;
}

my ($old, $new) = @ARGV;
my $devices = load_nics();

unless (defined $devices->{$old}) {
   die "No such device named '$old'.\n";
}
if (defined $devices->{$new}) {
   die "Device named '$new' already exists.\n";
}

system ("/sbin/ip", "link", "set", "dev", $old, "name", $new);
my $exit_value = $? >> 8;
if ($exit_value != 0) {
   die "Unable to rename device: $!";
}
exit (0);

# load_nics
#
# @returns hash (key = name of device, value = arrayref [ mac, device ID ]
sub load_nics {

   my $devices = {};

   open SHOW, "shownics -md |" or die "Unable to run shownics : $!";
   while (my $line = <SHOW>) {
      chop $line;
      my ($name, $mac, $device) = split (/\t/, $line);
      $devices->{$name} = [ $mac, $device ];
   }  
   close SHOW;
   
   return $devices;

}